[Biggermens]

Hello

I understand the dangers and how it works it just I want to do lost wax castings with a wax model of my part and sand castings for more simple parts.
all i am using is aluminium

All I wanted to know is what a good recipe the slurry. If I can use plaster of paris ??

I will start with that I will leave the sand casting for later.

Thanks

Paprjam good job on the rose it looks good .

[paprjam]

Thanks, that the mixed results. There are supposed to be 3 of them, the other 2 didn't fill.

[DMF_TomB]

PreHeating Molds will help them fill and also make sure there is not any water or moisture in the mold.

I had a Cast Iron mold I was pouring white hot cast iron in. It had a few drops of moisture in it. It exploded like a burst of fireworks with the dozens of flying sparks bursting again after 10 feet. It is no fun being in the middle of a burst of molten metal.

A large weed burner type propane torch heating the mold till it is well above the boiling point of water and it is no longer giving off steam might be a safer ideal and the heat will help the mold fill better.

[paprjam]

I heated the mold with the weed burner. Those things put out some heat.
I was doing an experiment with the wax, different sized spues. The 2 smaller ones didn't fill. The roses were little candles from the craft store. I think the brass cooled some while I was removeing the dross. I didn't check the temp.

[awerby]

[QUOTE=Biggermens;744495]Hello

I understand the dangers and how it works it just I want to do lost wax castings with a wax model of my part and sand castings for more simple parts.
all i am using is aluminium

[Have you already succeeded in melting aluminum?]

All I wanted to know is what a good recipe the slurry. If I can use plaster of paris ??

[Slurry and investment are different. Slurry is a permanently liquid material used for ceramic shell casting; investment is poured into a flask around the wax pattern and then it sets. You can't dip your parts in investment, and you can't invest with slurry.

Plaster of Paris is the material that holds the aggregate together. It's like the cement in concrete; too much binder and not enough aggregate will lead to weak investment that cracks up. A common mixture is by volume: 2 parts sand to 1 part plaster. The amount of water is a critical factor, though. Too much water will leave the mixture weak, with lots of "water trails" that destroy your detail. Also the sand will settle out. Too little water, and the mixture's too thick, plus it sets too fast. But it's not really possible to give you exact figures for the amount of water to use without knowing the moisture content of your aggregate. Also, the hardware-store Plaster of Paris that comes in little boxes is usually old and somewhat hydrated; you should get this in 100 or 50 lb sacks from a masonry supply house.]

I will start with that I will leave the sand casting for later.

[Good plan. Make sure you've got a kiln that can handle the moisture and fumes, that you can easily get your mold in and out of, and that won't choke everybody in your house when it gets going. Remember every speck of carbon residue should be consumed in the burnout, which should get up to at least 1000F; if there's anything left to burn down in the mold, it will spray molten aluminum all over the place as it erupts back out the pour-cup.]


Andrew Werby
www.unitedartworks.com